The present invention relates to testing closed fluid systems, and more particularly to an apparatus and method for testing, filling and purging entrained gas from closed fluid systems such as engine coolant systems.
Pressure testing the fluid tightness of closed fluid systems is primarily used in connection with automotive systems such as engine cooling systems, hydraulic brake systems, hydraulic clutch systems, hydraulic power steering systems, and air conditioning coolant systems. For example, most automotive internal combustion engines utilize a liquid cooling system comprising water and additives such as propylene glycol to maintain the engine within an optimum temperature range for operating efficiency. Such cooling systems generally employ a water pump which serves to circulate liquid coolant through flow paths located within the engine block where heat is transferred from the operating engine to the coolant, and then through a radiator where heat transfer occurs between the liquid and the atmosphere. With the advent of smaller engines having relatively high horsepower, more intricate cooling passages are necessary within the engine block. Additionally, the use of smaller radiators due to considerations of cost and sizing limitations, and higher operating temperatures for the engines results in a considerable amount of heat developed by the engine which must be dissipated through a relatively small radiator surface area. As a consequence, it is more important than ever to eliminate air pockets in the system as well as entrained air in the coolant so as to avoid "hot spots" from developing in the engine.
Since the cooling system of an automobile is designed to be a closed system, any minor leaks present in the flow path will reduce the efficiency of the system and may result in excessive coolant loss. As coolant is lost through leaks, the capability of the system to keep the engine temperature within an optimum range for operating efficiency is decreased, and if enough coolant is lost, overheating occurs with resultant damage to the engine. It is thus desirable that the cooling systems of internal combustion engines should be tested periodically on a regular basis in order to access the integrity of the system by detecting the presence of leaks, and filling the coolant system with fresh liquid coolant. Additionally, it is desirable to accomplish this testing and filling operation without creating air pockets in the system and without entraining a significant amount of air in the system fluid. This latter requirement is particularly advantageous with respect to the hydraulic fluid systems noted above relating to brake, clutch, and steering systems.
Various devices are known that are designed to test the fluid tightness of engine coolant systems, some examples are disclosed in the following United States patents:
______________________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ 3,207,254 D'Espinassy De Venel Sept. 21, 1965 3,623,372 Markey Nov. 30, 1971 3,650,147 Moyer Mar. 21, 1972 4,114,425 Hicks Sept. 19, 1978 4,235,100 Branchini Nov. 25, 1980 4,458,523 Moyer July 10, 1984 4,494,402 Carney Jan. 22, 1985 4,574,620 Cohl March 11, 1986 4,782,689 DeRome Nov. 8, 1988 ______________________________________
It is also desirable in some circumstances to accomplish the filling operation by drawing liquid from multiple reservoirs in a predetermined sequence. This is typically desired, for example, when a specific amount of coolant additive is to be added to an automotive cooling system during filling. If both additive and coolant were drawn from a single reservoir, it would be possible that some additive would remain diluted in that single reservoir.